1. Field of the Invention
The present invention relates to a virtual router distributed over a carrier network and a method for the routing of packets among several virtual local area networks relying on a switching network whose graph may be variable owing to the mobility of its nodes.
The expression “distributed virtual router” is used to designate the routing method. The underlying switching network is also known as a “carrier network”.
The nodes of the network communicate with one another for example by means of arteries whose configuration or existence may evolve over time, leading to a mobility of the nodes.
The invention can be applied especially to IP format packets of the Internet protocol.
The present invention can be applied for example in ATM type networks.
It can be applied to the emulation of routing in all networks using switching techniques.
2. Description of the Prior Art
In the prior art, the routing is done by means of a piece of equipment known as a router that relays the packets entering a junctor of this equipment towards an output junctor as a function of the destination IP address of the packet and as a function of the routing table.
When the routing is done between a large number of local area networks at very great distances from one another, a meshed network of routers consisting of access routers and transit routers is generally used.
A configuration of this kind has certain drawbacks, especially the following ones:
1) the transit time of a packet in the network is adversely affected by the large number of routers to be crossed,
2) the notion of quality of service (QoS) is not taken into account.
One way to overcome the above-mentioned drawbacks consists for example in integrating the IP routing (level 3) with a switching technology (level 2) such as the ATM (asynchronous transfer mode) switching. Three lines of development have been emphasized.
For example, what is called the gigarouter technology achieves a routing function at the core of a switch in taking account of the destination IP address in the switching process. In the ATM context, the destination IP address is taken into account during the translation of logic channels.
The label-switching technology identifies the flows within the IP traffic by a process of signalling associated with these flows of labels used by the level 2 switching. Applied to the ATM, a logic path indicator VPI/VCI is associated with a flow. This technology is being standardized at the IETF under the name of multiprotocol label switching (MPLS).
The technology known as “local area network and routing emulation” is used to create virtual circuits that directly connect the communications applications (short circuits) in using a specific protocol that defines customer entities, server entities, connections between these entities and rules for making short circuits between customers. In the ATM context, this technology is covered by a standard known as local area network emulation (LANE) and multiprotocol over ATM or MPOA.
This technology relies on the implementation of essential centralized functions of servers, flow routers with short lifetimes capable of being duplicated or even triplicated to provide minimum redundancy. However, when the network is subdivided into several non-interconnected components, there is no certainty that each component will have all the functions essential to the service nor that when two networks are combined, the redundant functions (offered by each of the components taken individually) will merge harmoniously, namely transparently for the user.
The object of the invention relates especially to a method of routing between virtual local area networks when the underlying switching network has a graph that may be variable owing to the mobility of its nodes, the network possibly being constituted by several components. A component is defined as a sub-network comprising at least two nodes that communicate with each other by arteries.
The number of components may be equal to the numbers of switches of the network.